[PATCH 0/2]

PATCH In review Finn Thain 3 participants 9 messages Oct 3, 2024 – Oct 20, 2024

Subsystems (4)

SPARC + UltraSPARC (sparc/sparc64) Real time clock (RTC) m68k architecture m68k on MVME147

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Finn Thain

author

2024-10-03 03:27 UTC #0 lore raw

cover [PATCH 0/2]

This series removes some duplicate RTC driver code. rtc-m48t59 is tweaked to bring it into equivalence with the RTC drivers in arch/m68k/mvme*. Then the latter drivers are removed and platform devices added to make use of the former.

The second patch depends upon the first, which will require some coordination between the maintainers of the RTC and m68k subsystems.

Finn Thain (2):
rtc: m48t59: Accommodate chips that lack a century bit
m68k: mvme147, mvme16x: Adopt rtc-m48t59 platform driver

 arch/m68k/configs/multi_defconfig   |   1 +
 arch/m68k/configs/mvme147_defconfig |   1 +
 arch/m68k/configs/mvme16x_defconfig |   1 +
 arch/m68k/include/asm/mvme147hw.h   |  19 +---
 arch/m68k/include/asm/mvme16xhw.h   |  18 +--
 arch/m68k/mvme147/config.c          |  54 ++++-----
 arch/m68k/mvme16x/Makefile          |   2 +-
 arch/m68k/mvme16x/config.c          |  56 ++++------
 arch/m68k/mvme16x/rtc.c             | 165 ----------------------------
 drivers/rtc/rtc-m48t59.c            |  31 +++---
 10 files changed, 67 insertions(+), 281 deletions(-)
 delete mode 100644 arch/m68k/mvme16x/rtc.c

Signature · 1 line

2.39.5

Finn Thain

author

2024-10-03 03:27 UTC #1 lore raw

PATCH 1/2 rtc: m48t59: Accommodate chips that lack a century bit

The m48t59 driver is needed by both SPARC and MVME systems. Linux on MVME uses 1970 as "year zero" rather than 1968 that's used on SPARC. Add support for the MVME convention. Otherwise, the RTC on non-SPARC systems can only read and write dates between 1900 and 1999.

Tested-by Daniel Palmer <[email protected]>

Signed-off-by Finn Thain <[email protected]>

---
 drivers/rtc/rtc-m48t59.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

drivers/rtc/rtc-m48t59.c +15 ~~-16~~

index f0f6b9b6daec..e2d882ea5c2f 100644
@@ -57,6 +57,17 @@ m48t59_mem_readb(struct device *dev, u32 ofs)
 	return readb(m48t59->ioaddr+ofs);
 }
 
+/*
+ * Sun SPARC machines count years since 1968. MVME machines running Linux
+ * count years since 1970.
+ */
+
+#ifdef CONFIG_SPARC
+#define YEAR0 68
+#else
+#define YEAR0 70
+#endif
+
 /*
  * NOTE: M48T59 only uses BCD mode
  */

@@ -82,10 +93,7 @@ static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm)
 		dev_dbg(dev, "Century bit is enabled\n");
 		tm->tm_year += 100;	/* one century */
 	}
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	tm->tm_year += 68;
-#endif
+	tm->tm_year += YEAR0;
 
 	tm->tm_wday	= bcd2bin(val & 0x07);
 	tm->tm_hour	= bcd2bin(M48T59_READ(M48T59_HOUR) & 0x3F);

@@ -108,10 +116,7 @@ static int m48t59_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	u8 val = 0;
 	int year = tm->tm_year;
 
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	year -= 68;
-#endif
+	year -= YEAR0;
 
 	dev_dbg(dev, "RTC set time %04d-%02d-%02d %02d/%02d/%02d\n",
 		year + 1900, tm->tm_mon, tm->tm_mday,

@@ -163,10 +168,7 @@ static int m48t59_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
 	M48T59_SET_BITS(M48T59_CNTL_READ, M48T59_CNTL);
 
 	tm->tm_year = bcd2bin(M48T59_READ(M48T59_YEAR));
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	tm->tm_year += 68;
-#endif
+	tm->tm_year += YEAR0;
 	/* tm_mon is 0-11 */
 	tm->tm_mon = bcd2bin(M48T59_READ(M48T59_MONTH)) - 1;

@@ -199,10 +201,7 @@ static int m48t59_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
 	unsigned long flags;
 	int year = tm->tm_year;
 
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	year -= 68;
-#endif
+	year -= YEAR0;
 
 	/* If no irq, we don't support ALARM */
 	if (m48t59->irq == NO_IRQ)

Signature · 1 line

2.39.5

Geert Uytterhoeven

maintainer

2024-10-03 07:47 UTC #2 lore raw

Re: [PATCH 1/2] rtc: m48t59: Accommodate chips that lack a century bit

Hi Finn,

Quoted 7 lines · Finn Thain

The m48t59 driver is needed by both SPARC and MVME systems. Linux on MVME uses 1970 as "year zero" rather than 1968 that's used on SPARC. Add support for the MVME convention. Otherwise, the RTC on non-SPARC systems can only read and write dates between 1900 and 1999.
Tested-by Daniel Palmer <[email protected]>
Signed-off-by Finn Thain <[email protected]>

Thanks for your patch!

Quoted 4 lines

drivers/rtc/rtc-m48t59.c +0 -0

@@ -57,6 +57,17 @@ m48t59_mem_readb(struct device *dev, u32 ofs)
        return readb(m48t59->ioaddr+ofs);

drivers/rtc/rtc-m48t59.c m48t59_mem_readb(struct device *dev, u32 ofs) · line 67

Quoted 10 lines

drivers/rtc/rtc-m48t59.c +8 -0

 }
 
+/*
+ * Sun SPARC machines count years since 1968. MVME machines running Linux
+ * count years since 1970.
+ */
+
+#ifdef CONFIG_SPARC
+#define YEAR0 68
+#else

+#define YEAR0 70

drivers/rtc/rtc-m48t59.c m48t59_mem_readb(struct device *dev, u32 ofs) · line 69

Quoted 1 line

drivers/rtc/rtc-m48t59.c +1 -0
+#endif

This causes a change in behavior on other non-SPARC platforms, if any out-of-tree platform exists that uses this driver.

So I'd rather use:

    #elif defined(CONFIG_VME)
    #define YEAR0 70
    #else
    #define YEAR0 0
    #endif

drivers/rtc/rtc-m48t59.c static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm) · line 96

Quoted 13 lines

drivers/rtc/rtc-m48t59.c +2 -4

+
 /*
  * NOTE: M48T59 only uses BCD mode
  */

@@ -82,10 +93,7 @@ static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm)
                dev_dbg(dev, "Century bit is enabled\n");
                tm->tm_year += 100;     /* one century */
        }
-#ifdef CONFIG_SPARC
-       /* Sun SPARC machines count years since 1968 */
-       tm->tm_year += 68;
-#endif
+       tm->tm_year += YEAR0;

Upon closer look, the driver uses platform data, so a better solution would be to add the year0 offset to struct m48t59_plat_data.

Another suggestion for improvement, not related to this patch, would be to differentiate among M48T59, M48T02, and M48T08 by using platform_driver.id_table and platform_device_id.driver_data, instead of m48t59_plat_data.type.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

Finn Thain

author

2024-10-03 22:20 UTC #3 lore raw

Re: [PATCH 1/2] rtc: m48t59: Accommodate chips that lack a century bit

Quoted 2 lines · Geert Uytterhoeven

Thanks for your patch!

Thanks for your review.

Quoted 15 lines

Quoted 4 lines
drivers/rtc/rtc-m48t59.c +0 -0
@@ -57,6 +57,17 @@ m48t59_mem_readb(struct device *dev, u32 ofs)
        return readb(m48t59->ioaddr+ofs);
drivers/rtc/rtc-m48t59.c m48t59_mem_readb(struct device *dev, u32 ofs) · line 67
Quoted 10 lines
drivers/rtc/rtc-m48t59.c +8 -0
 }
 
+/*
+ * Sun SPARC machines count years since 1968. MVME machines running Linux
+ * count years since 1970.
+ */
+
+#ifdef CONFIG_SPARC
+#define YEAR0 68
+#else
+#define YEAR0 70

Quoted 5 lines

drivers/rtc/rtc-m48t59.c m48t59_mem_readb(struct device *dev, u32 ofs) · line 69
Quoted 1 line
drivers/rtc/rtc-m48t59.c +1 -0
+#endif
This causes a change in behavior on other non-SPARC platforms, if any out-of-tree platform exists that uses this driver.

I'm unaware of any need to support out-of-tree code. Do you see think such a requirement would be feasible somehow? Is this documented somewhere?

Quoted 8 lines

So I'd rather use:

    #elif defined(CONFIG_VME)
    #define YEAR0 70
    #else
    #define YEAR0 0
    #endif

That is a Y2K bug, right?

Quoted 8 lines

drivers/rtc/rtc-m48t59.c +1 -0

+
 /*
  * NOTE: M48T59 only uses BCD mode
  */

@@ -82,10 +93,7 @@ static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm)
                dev_dbg(dev, "Century bit is enabled\n");
                tm->tm_year += 100;     /* one century */
        }

Quoted 9 lines

drivers/rtc/rtc-m48t59.c static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm) · line 96
Quoted 5 lines
drivers/rtc/rtc-m48t59.c +1 -4
-#ifdef CONFIG_SPARC
-       /* Sun SPARC machines count years since 1968 */
-       tm->tm_year += 68;
-#endif
+       tm->tm_year += YEAR0;
Upon closer look, the driver uses platform data, so a better solution would be to add the year0 offset to struct m48t59_plat_data.

I agree.

Quoted 5 lines

Another suggestion for improvement, not related to this patch, would be to differentiate among M48T59, M48T02, and M48T08 by using platform_driver.id_table and platform_device_id.driver_data, instead of m48t59_plat_data.type.

Yes, that's well out-of-scope I think.

Alexandre Belloni

maintainer

2024-10-03 08:10 UTC #4 lore raw

Re: [PATCH 1/2] rtc: m48t59: Accommodate chips that lack a century bit

In reply to Finn Thain

Hello,

Quoted 34 lines · Finn Thain

The m48t59 driver is needed by both SPARC and MVME systems. Linux on MVME uses 1970 as "year zero" rather than 1968 that's used on SPARC. Add support for the MVME convention. Otherwise, the RTC on non-SPARC systems can only read and write dates between 1900 and 1999.
Tested-by Daniel Palmer <[email protected]>
Signed-off-by Finn Thain <[email protected]>
---
 drivers/rtc/rtc-m48t59.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)
drivers/rtc/rtc-m48t59.c +11 -0
index f0f6b9b6daec..e2d882ea5c2f 100644
@@ -57,6 +57,17 @@ m48t59_mem_readb(struct device *dev, u32 ofs)
 	return readb(m48t59->ioaddr+ofs);
 }
 
+/*
+ * Sun SPARC machines count years since 1968. MVME machines running Linux
+ * count years since 1970.
+ */
+
+#ifdef CONFIG_SPARC
+#define YEAR0 68
+#else
+#define YEAR0 70
+#endif
+
 /*
  * NOTE: M48T59 only uses BCD mode
  */

drivers/rtc/rtc-m48t59.c static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm) · line 97

Quoted 9 lines

drivers/rtc/rtc-m48t59.c +1 -4

@@ -82,10 +93,7 @@ static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm)
 		dev_dbg(dev, "Century bit is enabled\n");
 		tm->tm_year += 100;	/* one century */
 	}
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	tm->tm_year += 68;
-#endif
+	tm->tm_year += YEAR0;

I'm super happy to see someone working on this, while you are it, can you use m48t59->rtc->start_secs and m48t59->rtc->set_start_time in probe instead of offsetting tm_year in read_time/set_time so we can later use device tree or any other mechanism to extend the range?

It is super funny because I was telling Geert that I wanted to get rid of this #ifdef CONFIG_SPARC two weeks ago at LPC. That could indeed then come from platform data.

Quoted 41 lines

drivers/rtc/rtc-m48t59.c +3 ~~-12~~

 	tm->tm_wday	= bcd2bin(val & 0x07);
 	tm->tm_hour	= bcd2bin(M48T59_READ(M48T59_HOUR) & 0x3F);

@@ -108,10 +116,7 @@ static int m48t59_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	u8 val = 0;
 	int year = tm->tm_year;
 
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	year -= 68;
-#endif
+	year -= YEAR0;
 
 	dev_dbg(dev, "RTC set time %04d-%02d-%02d %02d/%02d/%02d\n",
 		year + 1900, tm->tm_mon, tm->tm_mday,

@@ -163,10 +168,7 @@ static int m48t59_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
 	M48T59_SET_BITS(M48T59_CNTL_READ, M48T59_CNTL);
 
 	tm->tm_year = bcd2bin(M48T59_READ(M48T59_YEAR));
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	tm->tm_year += 68;
-#endif
+	tm->tm_year += YEAR0;
 	/* tm_mon is 0-11 */
 	tm->tm_mon = bcd2bin(M48T59_READ(M48T59_MONTH)) - 1;

@@ -199,10 +201,7 @@ static int m48t59_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
 	unsigned long flags;
 	int year = tm->tm_year;
 
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	year -= 68;
-#endif
+	year -= YEAR0;
 
 	/* If no irq, we don't support ALARM */
 	if (m48t59->irq == NO_IRQ)

Signature · 1 line

2.39.5

Signature · 3 lines

Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Finn Thain

author

2024-10-03 22:31 UTC #5 lore raw

Re: [PATCH 1/2] rtc: m48t59: Accommodate chips that lack a century bit

Quoted 41 lines · Alexandre Belloni

Quoted 40 lines · Finn Thain
The m48t59 driver is needed by both SPARC and MVME systems. Linux on MVME uses 1970 as "year zero" rather than 1968 that's used on SPARC. Add support for the MVME convention. Otherwise, the RTC on non-SPARC systems can only read and write dates between 1900 and 1999.
Tested-by Daniel Palmer <[email protected]>
Signed-off-by Finn Thain <[email protected]>
---
 drivers/rtc/rtc-m48t59.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)
drivers/rtc/rtc-m48t59.c +11 -3
index f0f6b9b6daec..e2d882ea5c2f 100644
@@ -57,6 +57,17 @@ m48t59_mem_readb(struct device *dev, u32 ofs)
 	return readb(m48t59->ioaddr+ofs);
 }
 
+/*
+ * Sun SPARC machines count years since 1968. MVME machines running Linux
+ * count years since 1970.
+ */
+
+#ifdef CONFIG_SPARC
+#define YEAR0 68
+#else
+#define YEAR0 70
+#endif
+
 /*
  * NOTE: M48T59 only uses BCD mode
  */
@@ -82,10 +93,7 @@ static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm)
 		dev_dbg(dev, "Century bit is enabled\n");
 		tm->tm_year += 100;	/* one century */
 	}
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	tm->tm_year += 68;

Quoted 9 lines

drivers/rtc/rtc-m48t59.c static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm) · line 97
Quoted 3 lines
drivers/rtc/rtc-m48t59.c +1 -1
-#endif
+	tm->tm_year += YEAR0;
 
I'm super happy to see someone working on this, while you are it, can you use m48t59->rtc->start_secs and m48t59->rtc->set_start_time in probe instead of offsetting tm_year in read_time/set_time so we can later use device tree or any other mechanism to extend the range?

Sure, I will look into it.

Quoted 4 lines

It is super funny because I was telling Geert that I wanted to get rid of this #ifdef CONFIG_SPARC two weeks ago at LPC. That could indeed then come from platform data.

I can't test any patches on SPARC, unless there's some way to do so using QEMU that would satisfy maintainers. (I rely on Daniel to test my patches on an MVME147 system.)

Finn Thain

author

2024-10-05 04:23 UTC #6 lore raw

Re: [PATCH 1/2] rtc: m48t59: Accommodate chips that lack a century bit

In reply to Alexandre Belloni

Quoted 6 lines · Alexandre Belloni

... while you are it, can you use m48t59->rtc->start_secs and m48t59->rtc->set_start_time in probe instead of offsetting tm_year in read_time/set_time so we can later use device tree or any other mechanism to extend the range?

That didn't work out as I'd hoped. I booted a patched kernel (diff below) under qemu-system-sparc64:

~ # for yyyy in 1970 1971 1999 2000 2024 2025 2068 2069 ; do date 01010101$yyyy ; hwclock --systohc --utc && hwclock --utc ; echo ; done Thu Jan 1 01:01:00 UTC 1970
Thu Jan 1 01:01:00 1970 0.000000 seconds

Fri Jan 1 01:01:00 UTC 1971
Tue Nov 24 18:32:44 1998 0.000000 seconds

Fri Jan 1 01:01:00 UTC 1999
Tue Nov 24 18:32:44 2026 0.000000 seconds

Sat Jan 1 01:01:00 UTC 2000
Sun Jan 2 23:29:16 2000 0.000000 seconds

Mon Jan 1 01:01:00 UTC 2024
Tue Jan 2 23:29:16 2024 0.000000 seconds

Wed Jan 1 01:01:00 UTC 2025
Thu Jan 2 23:29:16 2025 0.000000 seconds

Sun Jan 1 01:01:00 UTC 2068
hwclock: RTC_SET_TIME: Numerical result out of range

Tue Jan 1 01:01:00 UTC 2069
hwclock: RTC_SET_TIME: Numerical result out of range

~ #

Here's the result from an unpatched kernel (v6.11):

Fri Jan 1 01:01:00 UTC 1971
Fri Jan 1 01:01:00 1971 0.000000 seconds

Fri Jan 1 01:01:00 UTC 1999
Fri Jan 1 01:01:01 1999 0.000000 seconds

Sat Jan 1 01:01:00 UTC 2000
Sat Jan 1 01:01:00 2000 0.000000 seconds

Mon Jan 1 01:01:00 UTC 2024
Mon Jan 1 01:01:00 2024 0.000000 seconds

Wed Jan 1 01:01:00 UTC 2025
Wed Jan 1 01:01:00 2025 0.000000 seconds

Sun Jan 1 01:01:00 UTC 2068
hwclock: RTC_RD_TIME: Invalid argument

Tue Jan 1 01:01:00 UTC 2069
hwclock: RTC_RD_TIME: Invalid argument

~ #

I'm afraid I don't see how we might avoid adding/subtracting in read_time/set_time given that we must avoid messing up the present date when users boot into an upgraded kernel.

arch/sparc/kernel/time_32.c +1 -0

index 08bbdc458596..41ae3d1aa12e 100644
@@ -255,6 +255,7 @@ static void mostek_write_byte(struct device *dev, u32 ofs, u8 val)
 static struct m48t59_plat_data m48t59_data = {
 	.read_byte = mostek_read_byte,
 	.write_byte = mostek_write_byte,
+	.start_year = 1968,
 };
 
 /* resource is set at runtime */

arch/sparc/kernel/time_64.c +1 -0

index 60f1c8cc5363..eceb3fadb71a 100644
@@ -544,6 +544,7 @@ static void mostek_write_byte(struct device *dev, u32 ofs, u8 val)
 static struct m48t59_plat_data m48t59_data = {
 	.read_byte	= mostek_read_byte,
 	.write_byte	= mostek_write_byte,
+	.start_year	= 1968,
 };
 
 static struct platform_device m48t59_rtc = {

drivers/rtc/rtc-m48t59.c +5 ~~-18~~

index f0f6b9b6daec..d7e1f79cd52b 100644
@@ -82,10 +82,6 @@ static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm)
 		dev_dbg(dev, "Century bit is enabled\n");
 		tm->tm_year += 100;	/* one century */
 	}
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	tm->tm_year += 68;
-#endif
 
 	tm->tm_wday	= bcd2bin(val & 0x07);
 	tm->tm_hour	= bcd2bin(M48T59_READ(M48T59_HOUR) & 0x3F);

@@ -108,11 +104,6 @@ static int m48t59_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	u8 val = 0;
 	int year = tm->tm_year;
 
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	year -= 68;
-#endif
-
 	dev_dbg(dev, "RTC set time %04d-%02d-%02d %02d/%02d/%02d\n",
 		year + 1900, tm->tm_mon, tm->tm_mday,
 		tm->tm_hour, tm->tm_min, tm->tm_sec);

@@ -163,10 +154,7 @@ static int m48t59_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
 	M48T59_SET_BITS(M48T59_CNTL_READ, M48T59_CNTL);
 
 	tm->tm_year = bcd2bin(M48T59_READ(M48T59_YEAR));
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	tm->tm_year += 68;
-#endif
+
 	/* tm_mon is 0-11 */
 	tm->tm_mon = bcd2bin(M48T59_READ(M48T59_MONTH)) - 1;

@@ -199,11 +187,6 @@ static int m48t59_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
 	unsigned long flags;
 	int year = tm->tm_year;
 
-#ifdef CONFIG_SPARC
-	/* Sun SPARC machines count years since 1968 */
-	year -= 68;
-#endif
-
 	/* If no irq, we don't support ALARM */
 	if (m48t59->irq == NO_IRQ)
 		return -EIO;

@@ -458,6 +441,10 @@ static int m48t59_rtc_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, m48t59);
 
 	m48t59->rtc->ops = &m48t59_rtc_ops;
+	m48t59->rtc->range_min = mktime64(1900, 1, 1, 0, 0, 0);
+	m48t59->rtc->range_max = mktime64(1999, 12, 31, 23, 59, 59);
+	m48t59->rtc->start_secs = mktime64(pdata->start_year, 1, 1, 0, 0, 0);
+	m48t59->rtc->set_start_time = true;
 
 	nvmem_cfg.size = pdata->offset;
 	ret = devm_rtc_nvmem_register(m48t59->rtc, &nvmem_cfg);

include/linux/rtc/m48t59.h +3 -0

index 9465d5405fe2..b01c514d7079 100644
@@ -56,6 +56,9 @@ struct m48t59_plat_data {
 	void __iomem *ioaddr;
 	/* offset to RTC registers, automatically set according to the type */
 	unsigned int offset;
+
+	/* value to be used to initialize rtc->start_secs */
+	time64_t start_year;
 };
 
 #endif /* _LINUX_RTC_M48T59_H_ */

Alexandre Belloni

maintainer

2024-10-20 20:18 UTC #7 lore raw

Re: [PATCH 1/2] rtc: m48t59: Accommodate chips that lack a century bit

Quoted 69 lines · Finn Thain

Quoted 6 lines · Alexandre Belloni
... while you are it, can you use m48t59->rtc->start_secs and m48t59->rtc->set_start_time in probe instead of offsetting tm_year in read_time/set_time so we can later use device tree or any other mechanism to extend the range?
That didn't work out as I'd hoped. I booted a patched kernel (diff below) under qemu-system-sparc64:
~ # for yyyy in 1970 1971 1999 2000 2024 2025 2068 2069 ; do date 01010101$yyyy ; hwclock --systohc --utc && hwclock --utc ; echo ; done Thu Jan 1 01:01:00 UTC 1970
Thu Jan 1 01:01:00 1970 0.000000 seconds
Fri Jan 1 01:01:00 UTC 1971
Tue Nov 24 18:32:44 1998 0.000000 seconds
Fri Jan 1 01:01:00 UTC 1999
Tue Nov 24 18:32:44 2026 0.000000 seconds
Sat Jan 1 01:01:00 UTC 2000
Sun Jan 2 23:29:16 2000 0.000000 seconds
Mon Jan 1 01:01:00 UTC 2024
Tue Jan 2 23:29:16 2024 0.000000 seconds
Wed Jan 1 01:01:00 UTC 2025
Thu Jan 2 23:29:16 2025 0.000000 seconds
Sun Jan 1 01:01:00 UTC 2068
hwclock: RTC_SET_TIME: Numerical result out of range
Tue Jan 1 01:01:00 UTC 2069
hwclock: RTC_SET_TIME: Numerical result out of range
~ #
Here's the result from an unpatched kernel (v6.11):
~ # for yyyy in 1970 1971 1999 2000 2024 2025 2068 2069 ; do date 01010101$yyyy ; hwclock --systohc --utc && hwclock --utc ; echo ; done Thu Jan 1 01:01:00 UTC 1970
Thu Jan 1 01:01:00 1970 0.000000 seconds
Fri Jan 1 01:01:00 UTC 1971
Fri Jan 1 01:01:00 1971 0.000000 seconds
Fri Jan 1 01:01:00 UTC 1999
Fri Jan 1 01:01:01 1999 0.000000 seconds
Sat Jan 1 01:01:00 UTC 2000
Sat Jan 1 01:01:00 2000 0.000000 seconds
Mon Jan 1 01:01:00 UTC 2024
Mon Jan 1 01:01:00 2024 0.000000 seconds
Wed Jan 1 01:01:00 UTC 2025
Wed Jan 1 01:01:00 2025 0.000000 seconds
Sun Jan 1 01:01:00 UTC 2068
hwclock: RTC_RD_TIME: Invalid argument
Tue Jan 1 01:01:00 UTC 2069
hwclock: RTC_RD_TIME: Invalid argument

Quoted 6 lines

~ #
I'm afraid I don't see how we might avoid adding/subtracting in read_time/set_time given that we must avoid messing up the present date when users boot into an upgraded kernel.

I'm pretty sure this is avoidable as this is exactly what the offset mechanism is trying to achieve. I guess the issue is in the RTC core because both range_min and start_secs are negative which has never been tested. My plan was to have unit tests for this but this never happened...

Signature · 3 lines

Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Finn Thain

author

2024-10-03 03:27 UTC #8 lore raw

PATCH 2/2 m68k: mvme147, mvme16x: Adopt rtc-m48t59 platform driver

In reply to Finn Thain

Both mvme147 and mvme16x platforms have their own RTC driver implementations that duplicate functionality provided by the rtc-m48t59 driver. Adopt the rtc-m48t59 driver and remove the other ones.

Tested-by Daniel Palmer <[email protected]>

Signed-off-by Finn Thain <[email protected]>

---
 arch/m68k/configs/multi_defconfig   |   1 +
 arch/m68k/configs/mvme147_defconfig |   1 +
 arch/m68k/configs/mvme16x_defconfig |   1 +
 arch/m68k/include/asm/mvme147hw.h   |  19 +---
 arch/m68k/include/asm/mvme16xhw.h   |  18 +--
 arch/m68k/mvme147/config.c          |  54 ++++-----
 arch/m68k/mvme16x/Makefile          |   2 +-
 arch/m68k/mvme16x/config.c          |  56 ++++------
 arch/m68k/mvme16x/rtc.c             | 165 ----------------------------
 9 files changed, 52 insertions(+), 265 deletions(-)
 delete mode 100644 arch/m68k/mvme16x/rtc.c

arch/m68k/configs/multi_defconfig +1 -0

index 638df8442c98..617ac93298f3 100644
@@ -506,6 +506,7 @@ CONFIG_RTC_CLASS=y
 CONFIG_RTC_DRV_MSM6242=m
 CONFIG_RTC_DRV_RP5C01=m
 CONFIG_RTC_DRV_GENERIC=m
+CONFIG_RTC_DRV_M48T59=m
 # CONFIG_VIRTIO_MENU is not set
 # CONFIG_VHOST_MENU is not set
 # CONFIG_IOMMU_SUPPORT is not set

arch/m68k/configs/mvme147_defconfig +1 -0

index 2248db426081..4a0928b3b842 100644
@@ -392,6 +392,7 @@ CONFIG_UHID=m
 CONFIG_RTC_CLASS=y
 # CONFIG_RTC_NVMEM is not set
 CONFIG_RTC_DRV_GENERIC=m
+CONFIG_RTC_DRV_M48T59=y
 # CONFIG_VIRTIO_MENU is not set
 # CONFIG_VHOST_MENU is not set
 # CONFIG_IOMMU_SUPPORT is not set

arch/m68k/configs/mvme16x_defconfig +1 -0

index 2975b66521f6..481fb2810f1e 100644
@@ -393,6 +393,7 @@ CONFIG_UHID=m
 CONFIG_RTC_CLASS=y
 # CONFIG_RTC_NVMEM is not set
 CONFIG_RTC_DRV_GENERIC=m
+CONFIG_RTC_DRV_M48T59=y
 # CONFIG_VIRTIO_MENU is not set
 # CONFIG_VHOST_MENU is not set
 # CONFIG_IOMMU_SUPPORT is not set

arch/m68k/include/asm/mvme147hw.h +1 ~~-18~~

index e28eb1c0e0bf..2b147ab1d189 100644
@@ -4,24 +4,7 @@
 
 #include <asm/irq.h>
 
-typedef struct {
-	unsigned char
-		ctrl,
-		bcd_sec,
-		bcd_min,
-		bcd_hr,
-		bcd_dow,
-		bcd_dom,
-		bcd_mth,
-		bcd_year;
-} MK48T02;
-
-#define RTC_WRITE	0x80
-#define RTC_READ	0x40
-#define RTC_STOP	0x20
-
-#define m147_rtc ((MK48T02 * volatile)0xfffe07f8)
-
+#define MVME147_RTC_BASE	0xfffe0000
 
 struct pcc_regs {
    volatile u_long	dma_tadr;

arch/m68k/include/asm/mvme16xhw.h +1 ~~-17~~

index cc7f5ae1220f..ff1126a51fbe 100644
@@ -24,23 +24,7 @@ typedef struct {
 
 #define mvmelp   ((*(volatile MVMElpPtr)(MVME_LPR_BASE)))
 
-typedef struct {
-	unsigned char
-		ctrl,
-		bcd_sec,
-		bcd_min,
-		bcd_hr,
-		bcd_dow,
-		bcd_dom,
-		bcd_mth,
-		bcd_year;
-} MK48T08_t, *MK48T08ptr_t;
-
-#define RTC_WRITE	0x80
-#define RTC_READ	0x40
-#define RTC_STOP	0x20
-
-#define MVME_RTC_BASE	0xfffc1ff8
+#define MVME_RTC_BASE	0xfffc0000
 
 #define MVME_I596_BASE	0xfff46000

arch/m68k/mvme147/config.c +23 ~~-31~~

85 lines not on this page · raw message

arch/m68k/mvme16x/Makefile +1 -1

index a8a368c2cbea..02f9e4ad8209 100644
@@ -3,4 +3,4 @@
 # Makefile for Linux arch/m68k/mvme16x source directory
 #
 
-obj-y		:= config.o rtc.o
+obj-y		:= config.o

arch/m68k/mvme16x/config.c +23 ~~-33~~

89 lines not on this page · raw message

arch/m68k/mvme16x/rtc.c deleted +0 ~~-165~~

165 lines not on this page · raw message

Signature · 1 line

2.39.5